Since active agents, like for example antibodies, have been developed so as to be active only in their native form, denatured active agents are often not effective and have to be avoided. Denaturation means a structural transformation of the biomolecules, for example proteins, which in most cases is connected with a loss of the biological function of said molecules. Denaturation may be the consequence of either physical or chemical influences. Thus, active agent formulations have to be developed which prevent the denaturation of drugs, i.e. stabilize them for example thermally, chemically and/or with respect to time.
Aggregating active agents may lead to ineffectiveness as well. Furthermore, aggregated and/or denatured particles, for example aggregated antibodies, may provoke a reaction of the immune system in the body and thus have to be either avoided in drugs or their percentage in the drug has to be minimized.
Denaturation of particles, for example antibodies, has per se to be avoided since it reduces the effectiveness. The aggregation of particles, for example antibodies, has per se to be avoided since it provokes a reaction of the immune system and may also lead to a reduction of effectiveness.
It is often unclear why a particle aggregates and/or denatures: Does a particle aggregate because it denatures, i.e. because it is not in its native form or does it aggregate in its native form and denatures afterwards? Thus, in order to comprehensively characterize the particles, it is often not sufficient to analyze merely the aggregation or merely the denaturation separately from each other.
With the inventive system and method the denaturation as well as the aggregation of particles may be measured. In particular, with the inventive system and method, the denaturation as well as the aggregation of particles may be measured virtually simultaneously (substantially simultaneously) or simultaneously.
The denaturation of particles is an “intra particle” procedure and may be measured with the inventive method and system by means of measuring the intrinsic particle fluorescence (for example tryptophan fluorescence, tyrosine fluorescence). Simultaneously, the aggregation of the particles, an “inter particle” procedure which changes the size of the particles, may be measured by means of scattering of unabsorbed light.
Since the scattering of light, for example the static scattering of light in the case of the Rayleigh scattering, depends on the sixth power of the size of the particle (radius), it is very suitable to measure the changes the particle size and thus the aggregation of particles. Said light scattering method is known and is used by many apparatuses and methods. In particular, the devices known from the prior art measure the scattered light of the particles at determined solid angles, i.e. the share of light which is scattered by a particle in a determined solid angle vis-à-vis the incident light. The larger the particles and the smaller the wavelength, the larger the intensity of the scattered light for a fixed, suitably determined angle becomes (cf. for example http://www.lsinstruments.ch/technolgy/static_light_scattering_sls/). Such a method is described for example in the application US 2014/0234865 A1.
From an increase in the scattered light, for example during increase in the temperature, these methods may conclude an amendment in size and thus aggregation of the particles. A person skilled in the field of light scattering procedures knows that it has to be avoided that the excitation light which is beamed onto particles to be examined gets into the detection optics. A skilled person will always construct corresponding apparatuses in such a manner that a direct detection of said excitation light is avoided or the excitation light is blocked, which requires significant technical effort. It is for example described in patent DE 10 2007 031 244 that reflections are undesired with respect to scattering light measurements and also reflections at glass cuvettes may lead to problems.
Thus, there is the need for an improved or alternative system or an improved or alternative method for measuring the stability and the aggregation of particles.